Cable sheath



April 30, 1935. l. BRANTHwAlTE CABLE SHEATH Filed oct. 29, 19:52

3 IN VEN TOR.

. A TTORNE YS.

Patented Apr. 30, 1935 UNITED STATES CABLE SHEATH Isaac Branthwaite, Passaic, N. J., assigner to The Okonite-Callender Cable Company, Incorporated, Paterson, N. J., a corporation of New Jersey Application October 29, 1932, Serial No. 640,172

3 Claims.` (Cl. 173-266) This invention is directed to an improvement in sheaths for electric power cables and embodies a construction in which the metal sheath vof the cable is strengthened at the seam or weld in the 5 process of extruding the lead or other metal sheath about the cable.

In the operation of electric power cables considerable pressure is built up within the sheath of the cable due to the heat generated when the cable is under load, and it has been found in practice that the sheath frequently bursts at the seam. As above noted the present invention is directed to a construction in which the seam or Weld is very much strengthened and the chances of such an occurrence reduced to a minimum.

' The accompanying drawing which is more or less diagrammatic shows a three conductor cable in sectional elevation, A designating the conductors of the cable, B the insulation, C the filler and D the sheath.. The sheath D is usually of lead or of a lead alloy and may be applied to the conductors in a lead press. The seam formed in the extruding operation is designated E. Under present practice care is exercised to make the wall of the sheath D of uniform thickness inzluding that portion of the wall at the seam or weld E. By the present invention, however, I propose materially to increase the wall thickness of the sheath D at the seam or weld E as compared with the wall thickness of the rest of the sheath, as I have indicated at F, thereby providing a sheath of increased strength at the seam.

It is to'be understood that the type of cable shown in the drawing is merely illustrative of my invention, the invention being applicable to single conductor cables as Well as multi-conductor and to oil filled cables and rubber insulated cables.

It is to be understood, furthermore, that the expression sheat as employedin this description is to be interpreted to mean a sheath applied closely about the insulation of the conductor or conductors as well as a sheath the inside diameter of which is appreciably larger than the outside diameter of the conductor or conductors so as to provide a reservoir forthe reception of oil under pressure surrounding the insulation of the conductor or conductors.

What I claim isz- 1. As an article of manufacture a tubular sheath for oil lled electric cables, the sheath 10 being composed of extruded soft metal and having a continuous longitudinal seam, the wall thickness of the sheath at the said seam being materially increased during the extruding operation as compared with the wall thickness of the remainder of the sheath, thereby to increase the resistance of ,the sheath to bursting at the seam due t0 pressure built up in the cable when under load.

2. An electric power cable comprising in combination a conductor, oil impregnated insulation for the conductor and a soft metal sheath having a continuous longitudinal seam 'extruded about the insulation of the conductor, the wall thickness of the sheath at the seam being materially greater than the wall thickness of the remainder of the sheath to increase the resistance of the sheath to bursting at the seam due to pressures built up in the cable when under load'.

3. The process which comprises extruding soft metal in a molten condition about a, cable conductor and insulation assembly to form a tubular casing about the assembly having a continuous longitudinal seam, controlling the metal ,flow during the extruding operation so that the wall thickness of the tubular casing at the seam will be materially greater than the wall thickness of the remainder of the casing to increase the resistance of the sheath to bursting at the seam due to pressure built up in the cable when under load.

ISAAC BRANTHWArI'E. 40 

